Core Viewpoint - OS Therapies is advancing its regulatory submissions for OST-HER2, focusing on obtaining marketing authorizations in the UK and US for the treatment of pulmonary metastatic osteosarcoma, with submissions expected in late 2025 and early 2026 [3][7]. Regulatory Update - The company has updated its regulatory filing sequence to prioritize the UK MHRA conditional Marketing Authorisation Application (MAA) submission, which is expected to be completed in December 2025, followed by the US FDA Biologics Licensing Application (BLA) submission in January 2026 [3][7]. - A conditional MAA Pre-Submission Request has been submitted to the MHRA, and the company anticipates receiving formal acceptance for a rolling review request soon [4]. Clinical Trial Insights - The information in the MHRA conditional MAA submission aligns closely with the planned US FDA BLA submission, with the exception of the acceptable comparator arm for efficacy data [5]. - The company aims to use immune activation biomarker data as a surrogate marker correlated with overall survival to support its Accelerated Approval request [5][7]. Company Background - OS Therapies is a clinical-stage oncology company focused on developing treatments for osteosarcoma and other solid tumors, with OST-HER2 being its lead asset [8]. - OST-HER2 has received several designations from the FDA, including Rare Pediatric Disease Designation and Fast-Track designation, and has shown statistically significant benefits in its Phase 2b clinical trial [8]. Future Developments - The company is also advancing its next-generation Antibody Drug Conjugate (ADC) platform, known as tunable ADC (tADC), which utilizes proprietary technology for enhanced drug delivery [9].